I read the latest announcements on this as it will no longer be possible to upload single 360 images to any set of GPS coordinates. We will be limited to adding such images to existing points of interest = pins on Google Maps.
It is correct that adding a photo using Google Maps you can only add photos on Listings, and please avoid to create fake listings only to attach a 360 in there.
However there are other options, explained in the article:
“You can also use apps made by other companies … (The list of 3rd party publishing tools featured on the Street View website is not exhaustive. There are multiple other apps with similar functionalities that you can find online)”